In paper milling operations, calcium chloride is commonly used as a colorant fixative that is applied to a raw paper base in the size press process of a papermaking machine. Typically the calcium chloride is added to a surface sizing composition containing a sizing agent such as starch or a starch derivative or a water soluble polymeric material. The calcium chloride enhances the image quality of the resulting print media when printed with pigmented inks by reacting with the pigment colorants in the deposited ink. Calcium ions interact with anionic pigments, and in this way the pigment colorant is made to stay on the outermost portion or surface of the print media, which increases the optical density of the image on the media and also reduces the dry time of the deposited ink. In order to obtain satisfactory print quality (PQ), the concentration of calcium chloride in a print media is typically about 6-8 Kg/T (ton) of paper. In some cases the calcium chloride loading is up to 12 Kg/T of paper. However, such high loadings of chloride-containing compounds can promote corrosion of the paper milling equipment used to produce the print media. In some cases the use of calcium chloride-containing treatment compositions reduces the life span of the non-stainless-steel-corrosion-resistant grade parts that are contacting with salt of the paper manufacturing equipment, such as sizing rolls for instance. The promotion of corrosion by paper treatment chemicals is particularly challenging in commercial paper manufacturing processes that operate as “closed loop” mills with lower consumption of fresh water.
There is continuing interest in the development of ways to produce print media that perform well with pigmented inks, particularly in the field of inkjet printing.